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A report from Annals of Rheumatic Diseases suggests that osteoarthritis (OA) may be two distinct diseases based on genetic studies of articular cartilage. (Citation source: https://buff.ly/2mNtUsL).
RNA sequencing of knee cartilage from 44 OA patients undergoing total knee replacement was compared to 6 additional patients with OA and 10 control patients with non-OA.
Unsupervised clustering identified two distinct OA groups: Group A with 24 patients (55%) and Group B with 18 patients (41%). These results were further validated by RT-qPCR in 16 further patients with OA.
Between group differences were found in complement activation, innate immune responses and altered Wnt and TGFβ signalling, but not for inflammatory cytokine expression.
Matrix changes in Group A were chondrogenic, in Group B they were non-chondrogenic with changes in mechanoreceptors, calcium signalling, ion channels and in cytoskeletal organisers. The gene expression changes predicted 478 potential biomarkers for detection in synovial fluid to distinguish patients from the two groups.
It is postulated that variations between these two categories of OA could be used to predict different responses to treatment, and may explain why treating osteoarthritis as a single condition has proven unproductive.